Method and measuring device for measuring recycled fibre pulp

ABSTRACT

A measuring device is provided that includes a camera, and an image-processing unit and a fractionating pipe. The receives a sample from recycled fibre pulp of a recycled fibre process and arranges the particles of the flowing sample in accordance with particle size. The measuring device processes the sample as at least two fractions according to particle size. The camera images at least one fraction. The image-processing unit receives images imaged by the camera and measures at least one parameter of an added substance in at least one imaged fraction.

FIELD

The invention relates to a method and a measuring device for measuring recycled fibre pulp in a recycled fibre process.

BACKGROUND

A recycled fibre line is also called an RCF line (ReCycled Fiber), and it refers to a production process by means of which raw material for printing paper is produced from wastepaper mainly for newspapers and magazines. The process may also be called de-inking. Pasteboard and paperboard may also be recycled and reused in a corresponding manner. The aim in the pulping, washing, dispersing and rewashing of the recycled fibre pulp process is to detach the fibres of the recycled fibre pulp from each other, to separate substances, such as printing ink, wax, glue, plastic, metallization etc., added to the paper at the different stages from the fibres, and to remove the added substances from the recycled fibre pulp. The processing is complicated by the fact that the quality of recycled paper varies according to from where and how the paper was collected. In addition, wastepaper contains impurities and its moisture content varies.

A sample may be taken from the recycled fibre process and subject it to hyper-washing, wherein the aim is particularly to remove ink present as free particles in the sample. Hyper-washed samples taken at the different stages of the recycled fibre process may be compared with the recycled fibre pulp at the different stages of the recycled fibre process, thus enabling the determination of the efficiency of the processing of the recycled fibre and the quality of the recycled fibre pulp.

Hyper-washing may be performed as a manual wash by taking a sample into a container of the desired size, on the bottom of which is a wire. However, different laboratories use different wires, usually between 50 to 200 meshes (aperture size about 70 μm to 300 μm). The sample on the wire is subjected to water rinsing, whereby the particles smaller than the mesh size of the wire flow out of the container.

A plurality of problems is associated with manual washing. For example, containers, wires, numbers of samples, the temperature of the rinsing water and the pressure of the rinsing water are different in different measurements (made in different locations), which results in the measurements not being comparable. In addition, conceptions of a properly or correctly performed hyper-wash vary depending on the manner of measurement and the performer of the measurement, although the washing time and the amount of water consumed are known to affect the end result.

Hyper-washing may also be performed with a device manufactured for this purpose. In this solution, too, a wire (between 50 and 200 mesh) is used, through which the pulp is filtered by means of running water. An image-processing program may be used to measure both the loose ink in the filtrate and the ink adhered to the fibres of the washed pulp.

Problems are associated with this solution, too. The material, manufacturing geometry and wear of the wires affect the filtration and, consequently, the measurement result. The manufacture and maintenance of identical wire geometries is impossible, since even microscopic differences in the wires affect the measurement, and the manufacturing geometry changes along with wear. In addition, since one sample may be measured only with one wire, the result obtained from the sample cannot be compared with measurements made on different wires. The reproducibility of the solution is not either very good.

BRIEF DESCRIPTION

It is the object of the invention to provide an improved method and a measuring device implementing the method.

This is achieved with a method of measuring recycled fibre pulp, in whose manufacture at least one of the following was used: paper, paperboard, pasteboard, at least one added substance having been transferred to the surface of the paper, paperboard, pasteboard. The method further comprises taking a sample from the recycled fibre pulp of the recycled fibre process into a fractionating pipe, arranging the particles of the flowing sample in the fractionating pipe in accordance with the particle size, processing the sample as at least two fractions according to the particle size, and measuring at least one parameter of at least one added substance in at least one fraction.

The invention also relates to a method of measuring recycled fibre pulp, in whose manufacture at least one of the following was used: paper, paperboard, pasteboard, ink having been transferred to the surface of the paper, paperboard, pasteboard. The method further comprises taking a sample from the recycled fibre pulp of the recycled fibre process into a fractionating pipe, arranging the particles of the flowing sample in the fractionating pipe in accordance with the particle size, processing the sample as at least two fractions according to the particle size, and measuring at least one parameter of the ink in at least one fraction.

The invention further relates to a measuring device for measuring recycled fibre pulp in a recycled fibre process, in whose manufacture at least one of the following was used: paper, paperboard, pasteboard, at least one added substance having been transferred to the surface of the paper, paperboard, pasteboard. The measuring device comprises a fractionating pipe arranged to receive a sample from the recycled fibre pulp of the recycled fibre process and to arrange the particles of the flowing sample in accordance with the particle size, a sensor and a signal processing unit, and the measuring device is arranged to process the sample as at least two fractions according to the particle size, the sensor is arranged to measure at least one fraction, the signal processing unit is arranged to receive a measuring signal from the sensor and determine at least one parameter of at least one added substance in at least one fraction measured.

The invention still further relates to a measuring device for measuring recycled fibre pulp in a recycled fibre process, in whose manufacture at least one of the following was used: paper, paperboard, pasteboard, ink having been transferred to the surface of the paper, paperboard, pasteboard. The measuring device comprises a fractionating pipe arranged to receive a sample from the recycled fibre pulp of the recycled fibre process and to arrange the particles of the flowing sample in accordance with the particle size, a sensor and a signal processing unit, and the measuring device is arranged to process the sample as at least two fractions according to the particle size, the sensor is arranged to measure at least one fraction, the signal processing unit is arranged to receive a measuring signal from the sensor and determine at least one parameter of the ink in at least one fraction measured.

Preferred embodiments of the invention are described in the dependent claims.

The method and measuring device of the invention bring forth a plurality of advantages. The measurement is independent of the wire, the manufacturing geometry of the wire and the change in the manufacturing geometry of the wire with time. The results of one measurement may be adapted to measurements made on different wires. The reproducibility of the solution is good and the measuring circumstances manageable.

LIST OF FIGURES

In the following, the invention will be described in more detail in connection with preferred embodiments with reference to the accompanying drawings, in which

FIG. 1 shows a recycled fibre process,

FIG. 2 shows a fractionator,

FIG. 3 shows an optical measurement,

FIG. 4 shows different fraction distributions, and

FIG. 5 shows a method flow diagram.

DESCRIPTION OF EMBODIMENTS

Let us first generally study a recycled fibre process by means of FIG. 1. First, raw material obtained from recycling, such as newspapers, leaflets or magazines, may be fed into a pulping subprocess 100, the raw material being mixed in a pulper comprised by said process with water such that the consistency of the recycled fibre pulp becomes for instance 5 to 18% depending on the pulping method used. The purpose of the pulping subprocess is to chemically and mechanically disintegrate the raw material into recycled fibre pulp, wherein the fibres and added substances, such as ink, are broken down and separated into separate particles.

The pulper may be a rotating pulper, for example, wherein the recycled fibre pulp rises up along with the wall of the cylindrical pulper and falls down by the action of gravity. During processing, the recycled fibre pulp is disintegrated into increasingly smaller parts and, finally, into fibres. The falling height of the recycled fibre pulp depends on the speed of rotation of the drum. The pulp may rotate in the pulper 20 to 40 minutes and, having passed the pulper, enters the sieve section of the pulping subprocess, wherein it is diluted to a level of 3.5%, for example. This means that the largest impurities and non-degradable objects, such as staples, bits of plastic, etc., may be separated from the recycled fibre pulp by means of openings (diameter e.g. about 1 cm) in the sieve section. The objects separated from the recycled fibre pulp end up in a refuse conveyor.

A plurality of chemicals may be fed into the pulping subprocess for separating the particles from each other. Sodium hydroxide is used to raise the alkalinity of recycled fibre pulp to the level pH 9 to 10, for example. Sodium hydroxide serves to swell the fibres and facilitate the detachment of printing ink, for example. Soluble silicate, i.e. sodium silicate, in turn, also improves the detachment of printing ink, for example, and prevents the reattachment of ink. At the same time, it buffers the pH to the desired level. Hydrogen peroxide, typically used for bleaching pulp, prevents the pulp from yellowing in connection with pulping. Other chemicals may be used in addition.

Next, the recycled fibre pulp may be washed in a washing subprocess 102. At this stage, the consistency of the recycled fibre pulp is usually lowered to a level of about 1%, for example. In the washing, flotation may be used, which removes small free particles from the recycled fibre pulp. In the washing, particles of all sizes are removed, but the majority of particles removed are in the size order of about 10 μm to 100 μm. In addition, the recycled fibre pulp may be filtered (filter opening e.g. 2 mm) for better removal of objects unsuitable for recycled fibre pulp.

A dispersing subprocess 104 serves to further chemically and mechanically detach ink particles adhered to the fibres of the recycled fibre pulp. For mechanical processing, the dispersing machine of the dispersing subprocess comprises a stator and a rotating rotor, whose blades process the pulp. When the pulp passes between the blades, its speed changes rapidly, whereby the fibres are subjected to mechanical stress, which detaches ink from the fibres. At the same time, the purpose is to detach sticky substances from the fibres and to reduce the particle size of added substances, such as ink particles.

Finally, the recycled fibre pulp may be washed once more in a second washing subprocess 106. In this washing, too, flotation may be used, which removes small free particles from the recycled fibre pulp.

Each subprocess 100 to 106 of the recycled fibre process may be controlled with a controller 108, to which measurement results may be fed from different points of the recycled fibre process. The controller 108 may utilize the measurement data concerning the subprocesses when optimising the operation of each subprocess separately or when optimising the cooperation of the different subprocesses in order to achieve an optimally good end product. The purpose of the recycled fibre process is to remove substances that are harmful to the recycled fibre pulp. Often the focus is on removing printing ink. The fraction in which the ink particles of the recycled fibre pulp are affects the removal of ink and is indicative of the operation/success of the deinking process. The size order of the free ink particles affects the degree to which free ink can be removed from the recycled fibre process.

A sample or samples may be taken at least before one subprocess 100 to 106, during at least one subprocess 100 to 106 or after at least one subprocess 100 to 106.

All in all, the aim in processing recycled fibre pulp is to detach the fibres of the recycled fibre pulp from each other, to detach substances, such as printing ink, wax, hydrophobic agents, plastic, metallization etc., added by transfer to the surface of paper, paperboard or pasteboard after the actual manufacture, and to remove the added substances from the recycled fibre pulp.

In the mechanical and chemical processing of the pulping subprocess and the dispersing subprocess, the aim is to optimize the following, among other things: how well the fibres are detached from each other, are fibres breaking in the pulping, how well ink is detached from the fibre and the filling materials and the coating paste, and into how fine particles the ink is split. The mechanical processing means of the pulping subprocess include, for example: speed of travel of the pulp in the drum, i.e. production speed, the consistency of the pulp in the drum, and the speed of rotation of the drum. The chemical processing means of the pulping subprocess include, for example: the pH of the pulp in the drum, based on the dosage of sodium hydroxide, for example, the proportion of silicate dosage, and the consistency of the pulp (amount of water).

In dispersing, the separation of fibres and ink can be affected primarily mechanically, including, among others: speed of travel of pulp passing through the dispersing subprocess, i.e. production speed, consistency of pulp in the dispersing subprocess, temperature of pulp in the dispersing subprocess, speed of rotation of rotor, and amount of power fed into rotor. The amount of power fed into the rotor is typically controlled by controlling the a between the rotor and the stator, through which the pulp has to be conveyed.

Many substances transferred to the surface also remain on the surface of the paper, paperboard or pasteboard. These include printing ink, plastic or metal, for example. An example of the use of metal is aluminium-coated paper. After being transferred to the surface, some substances may be partly or entirely absorbed inside the paper. These may include wax, some (printing) inks and hydrophobic substances (such as glue).

The substance to be added may be transferred to the surface of the paper, paperboard or pasteboard by printing, spraying, spreading or brushing. In addition, an added substance may be transferred by various evaporation methods. The transfer may also be performed by immersing the paper, paperboard or pasteboard into the added substance, or the added substance may be glued or melted so that it sticks to the paper, paperboard or pasteboard.

It is common to the transfer that the paper, paperboard or pasteboard is finished per se, and a substance is transferred to its surface to one or both sides from outside the paper, paperboard or pasteboard often according to the purpose of use. Thus, the paper, paperboard or pasteboard has already left the paper machine and possibly also the paper mill. The finished paper, paperboard or pasteboard can then be transferred to a process, wherein the added substance is transferred to the surface of the paper, paperboard or pasteboard. The finished paper, paperboard or pasteboard may be transferred to a printing process, a conversion process etc. For example, if a package containing liquid is to be made from paperboard, the finished paperboard may be coated with plastic, and a container of the desired shape may be formed from the plastic-coated paperboard, and the container may be closed by gluing after filling. In addition, text and/or images may be printed onto the surface of the paperboard or plastic by means of ink. The paperboard container of this example may contain three different added substances: plastic, glue and ink.

FIG. 2 shows an apparatus for performing fractionation and operating like a chromatograph. A sample taken from the recycled fibre process may be fed through a valve 202 to a pipe 204, wherein the pressure, flow and temperature of water pushing the sample forwards may be adjusted by an adjuster 200. The desired chemical, which may be colouring agent for facilitating or enabling the measurement of the added substance, for example, may also be added to the sample through the valve 202. For example, the fibres may be coloured dark with a hydrophobic colouring agent, whereby the wax in the sample is not coloured and remains lighter.

The length of the pipe 204 performing the fractionation may be up to dozens or hundreds of metres, and its diameter may be from a few millimetres up to dozens of centimetres. The pipe 204 may be manufactured from a polymer, such as plastic, metal or the like. When the sample, which is a suspension, flows in the pipe 204, the solid particles of the sample are arranged in accordance with the particle size such that the larger particles are accumulated in the front part of the sample, the smallest particles being accumulated in the rear part of the sample. Thus, large particles flow more rapidly than small particles. The particles of the sample may be arranged in fractions according to the particle size, each of them comprising particles between the desired upper limit and lower limit.

The flowing sample may be imaged by means of at least one camera 206 and a source 208 of optical radiation. Optical radiation means electromagnetic radiation from ultraviolet (about 50 nm) to infrared (about 200 μm). The image or images may be transferred from the camera 206 to an image-processing unit 210, wherein the image or images generated may be transferred to a display 212. The image-processing unit 210 comprises a processor, memory and one or more computer programs required for performing image processing. The image or images may be transferred to the display 212 also directly from the camera 206 without processing performed in the image-processing unit 210. Each image may a fixed image or a video image. Each fixed image may present one fraction or an image presenting one fraction may be generated or selected from the group of images. The video image, in turn, may be a sequence of fixed images presenting shots from the front end of the sample to the rear end of the sample. In this case, when progressing from the first image (an image of the largest particles at the front end of the sample) image-by-image forwards, the average size of particles diminishes. In addition, the consistency of the fractions may be measured optically by utilizing the attenuation of optical radiation and, optionally, also the change in polarization.

Fractions may be taken from the samples into sample vessels 214 to 220, which may total N, wherein N is a positive integer and N is equal to or more than 2. Each fraction in a sample vessel 214 to 220 may be measured in a laboratory or the fractions may be measured as a sample flowing in the fractionating pipe 204 by using one or more optical measuring methods.

The measuring device may further comprise a cake formation unit 222 for converting the fractions in the vessels 214 to 220 into cakes 224. The cake unit 222 may comprise a container with a wire at the bottom and a drying device, such as a suction unit, and a furnace for drying the fraction filtered with the wire into solid substance.

Measurements descriptive of the characteristics of fibres include for instance measurement of the length of fibre, measurement of the length distribution of the fibres, measurement of the number of fibre bundles, and brightness measurement. Of these, brightness measurement may also measure ink characteristics (ink is adhered to the fibres).

Optical measurements of the characteristics of fibres may be performed by spectroscopy or by means of image analysis, and the measurements may be directed to a flowing sample or cakes made from sample fractions. The optical measurements may be measurements of absorption, reflectivity or scattering, wherein the polarization of optical radiation may be utilized.

The size of a particle, such as the length of a fibre or the diameter of an ink particle may be measured by using a line or matrix camera. The measurement may concern the number, portion, size or size distribution of free ink particles and to the number, portion, size or size distribution of ink particles adhered to fibres.

Measurement of the total ink in the pulp, i.e. the effective ink, may be performed by using measurement of optical radiation, which is the ERIC (Effective Residual Ink Concentration) method, for example. In this case, optical radiation on the desired band is directed to the pulp or cake, and reflected radiation is measured. Optical radiation may be infrared radiation, whose band may be selected such that the absorption coefficient of the ink in the pulp on the band used is higher than that of the fibres or other particles in the pulp. The band of infrared radiation may be between 700 nm and 1,500 nm, however, not being restricted thereto.

In addition, the amount or portion of ink adhered to the fibres and the amount or portion of free ink detached from fibres may be measured from the recycled fibre pulp. The measurement may be performed optically in such a manner that an image is generated, from which the number, portion and/or interrelationship of particles of different sizes and colours may be determined by means of a suitable image-processing program. Such a solution is described in U.S. Pat. No. 6,010,593, which describes this measurement in more detail.

FIG. 3 shows the general principle of optical measuring methods. Recycled fibre pulp 300 is directed to a transparent pipe 302 at the wavelength used in the optical measurement. As the recycled fibre pulp proceeds in the pipe 302, the recycled fibre pulp is illuminated with optical radiation generated by a source 304 of optical power. The optical power source 302 may be a led, a incandescent lamp, a gas discharge lamp, a laser or the like, and the optical power source may illuminate the target in a pulse-like manner or continuously. A camera 306, which may be a CCD camera (Charge Coupled Device) or a CMOS camera (Complementary Metal Oxide Semiconductor), for example, captures an image or images from the recycled fibre pulp 300 in the pipe 302, either from the same side where the optical power source is located, or from the opposite side. In addition, the camera 306 may be used to image by using radiation scattered from the recycled fibre pulp. An image-processing unit 308 may control the imaging and the illumination of the target and perform image processing and analysis. In the measurement of the length of fibres and the size of ink particles, a capillary pipe having a diameter of from less than one millimetre to a couple of millimetres may be used as the pipe 302. In other measurements, the diameter of the pipe 302 may be larger, up to dozens of centimetres.

Instead of the camera 306, a spectrometer may be used as the sensor 206 for determining the spectrum of the optical radiation reflected by each fraction. From the spectrum, the colour, brightness of the particles etc. and thus, the desired parameter to be measured, may be determined.

In contrast to what is shown in FIG. 3, the source 304 may direct a suitable energy to each fraction for achieving an acoustic response signal in the particles of the sample. The source 304 may be for instance a laser whose optical radiation causes acoustic oscillation of the particles. Similarly, instead of the camera 306, the sensor 206 may detect acoustic oscillation. Usually, acoustic oscillation is ultrasound. The frequency, amplitude and/or phase of acoustic radiation depend on the characteristics of the particles, i.e. the parameter to be measured.

FIG. 4 shows attenuation of optical radiation as a function of the amount of water run in the fractionating pipe. Curve 400 shows measurement before the washing subprocess of the recycled fibre process, curve 402 shows hyper-washing performed on a wire, and curve 404 shows the measurement result after the washing subprocess of the recycled fibre process. The vertical axis shows optically measured attenuation ATT and the horizontal axis shows the amount L of water run in litres. The attenuation ATT may be proportional to the consistency of the sample and thus, to the dry substance content in the different parts of the sample. The amount of water is inversely proportional to the size of the particles and it may be measured by initiating the measurement as the sample enters the fractionating pipe and measuring the amount when the desired point or fraction of the sample is run to a measurement point. The measurement point may be an area in the imaging sector of the camera. The more water is run in the fractionating pipe, the longer becomes the distribution of the sample and the more accurately the particles of different sizes are distinguished from each other. The length l of a sample may be assesses from the litre amount as follows:

l=(M1−M0)/A,

wherein M1 is the rear limit of the last fraction (in the example of FIG. 4, about 20 L=20 dm³). M0 is the start of the fractionation (in the example of FIG. 4 about 16 L=16 dm³), and A is the cross-sectional area of the fractionating pipe (in the example of FIG. 4 about 0.08 dm³). Thus, the length of the fractionated sample in the example of FIG. 4 becomes 200 dm=20 m. When the sample was taken, the sample was only about 25 cm long, and thus the fractionating pipe has stretched the sample under the fractionation to about 75-fold. If the sample flows about 1 m/s, the sample passes the optical measurement in about 20 seconds. If the camera captures images at 20-ms intervals, which corresponds to imaging at 2-mm intervals, 1,000 fixed images are obtained from the sample, i.e. 1,000 imaged fractions, which, presented in succession at the imaging speed, produce 20 s of video image. Only a few fractions are required, for instance four (FR1 to FR4), whereby each result measured from the fractions may correspond to the average of at most 250 images of the particles in the sample. Similarly, each fraction may be displayed with one representative image without averaging. In any case, the limits and amounts of fractions may be selected freely from the images captured.

A manner of dividing fractions is presented in FIG. 4 and this example utilizes four fractions. Fraction FR1 of the largest particles comprises particles in a litre amount of between 15.6 L to 16.3 L (in the order of 5 mm to 2 mm, for example), fraction FR2 of the second largest particles comprises particles in a litre amount of between 16.3 L and 17.5 L (in the order of 2 mm to 0.5 mm, for example), fraction FR3 of the second smallest particles comprises particles in a litre amount of between 17.5 L to 18.3 L (in the order of 0.5 mm to 0.1 mm, for example), and fraction FR4 of the smallest particles comprises particles in a litre amount of between 18.3 L and 20.4 L (in the order of 0.1 mm to 0.005 mm, for example).

In the case of FIG. 4, fraction FR1 of curve 400 may comprise flakes, fraction FR2 may comprise long fibres, fraction FR3 may comprise short fibres and FR4 may comprise ink particles, fine material and possible other small material particles, of which ink particles are usually significant as regards the reuse of recycled fibre pulp. The ink particles of fraction FR4 are in the order of 10 μm to 100 μm, which is usually largely removed in the washing subprocess of the recycled fibre process or which should be removed (almost) entirely in hyper-washing. This kind of result can be seen from curve 402, which presents the result of a hyper-wash performed on a wire. Since no particles are left in fraction FR4 in a complete hyper-wash, fraction FR4 of curve 400 may be given zeroes as predetermined values in the image-processing unit and thus consider the distribution thus obtained as reference for the washing to be prepared in the recycled fibre process. If the different fractions of the sample are collected into containers 214 to 220, as FIG. 2 shows, the contents of containers 214 to 218 may be combined (in this case, the fraction of container 220 is filtered off from the sample), whereby also a concrete reference is obtained from the hyper-washed sample. The measurement result 404 of the sample taken from the washing subprocess 102 (or 106) of the recycled fibre process may be compared with the reference, which is according to the distribution 400 in fractions FR1 to FR3 and has a constant value of 0 in fraction FR4. The comparison may be performed by means of correlation, for example. If the difference between the reference and the measurement result 404 is larger than a predetermined threshold value, the recycled fibre process does not operate adequately well, and the quality of the end product does not fulfil the desired quality requirements. In this case, the operation of the recycled fibre process has to be enhanced. If the difference is smaller than the threshold value, the operation of the recycled fibre process can be considered optimized and the quality of the end product sufficiently good.

Generally, any real subprocess of the recycled fibre process can be compared with a corresponding reference. In this case, the measurement of at least one parameter of at least one added substance may be performed by determining the difference between the distribution of at least one fraction measured after the desired subprocess and a predetermined distribution. The predetermined distribution thus depicts the desired distribution after the desired subprocess of the recycled fibre process.

The sample may be processed as at least two fractions by imaging the different particle sizes of the sample flowing in the fractionating pipe 204 with the camera 206, and generating at least one image representing at least one fraction with the image-processing unit 210 from the images generated by the camera 206. Alternatively or in addition, at least two fractions may be generated from the sample flowing in the fractionating pipe 204 into the containers 214 to 220 and image at least one fraction in one of the containers 214 to 220 with the camera 206. Furthermore, alternatively or in addition, a cake 222 may be generated from at least one fraction and image the at least one cake generated from the fraction with the camera 206.

The parameter to be measured may represent the portion in the sample of at least one added substance attached to the fibres. The parameter to be measured may also represent the portion in the sample of at least one added substance detached from the fibres. In addition, both above-mentioned parameters may be measured.

FIG. 5 shows a flow diagram of the method. In step 500, a sample is taken from the recycled fibre pulp of the recycled fibre process into a fractionating pipe. In step 502, the particles of the flowing sample are arranged in accordance with particle size in the fractionating pipe. In step 504, the sample is processed as at least two fractions according to the particle size. In step 506, at least one parameter of at least one added substance of at least one fraction is measured.

Although the invention is described herein with reference to the examples in accordance with the accompanying drawings, it will be appreciated that the invention is not to be so limited, but may be modified in a variety of ways within the scope of the appended claims. 

1. A method of measuring recycled fibre pulp, in the manufacture of which at least one of the following was used: paper, paperboard, pasteboard, and at least one added substance having been transferred to the surface of the paper, paperboard, pasteboard, the method comprising: taking a sample from the recycled fibre pulp of the recycled fibre process into a fractionating pipe; arranging the particles of the flowing sample in accordance with the particle size in the fractionating pipe; processing the sample as at least two fractions according to the particle size in the fractionating pipe; and measuring, with a sensor, at least one parameter of the at least one added substance of the at least one fraction.
 2. A method of measuring recycled fibre pulp, in the manufacture of which at least one of the following was used: paper, paperboard, pasteboard, and ink having been transferred to the surface of the paper, paperboard, pasteboard, the method comprising: taking a sample from the recycled fibre pulp of the recycled fibre process into a fractionating pipe; arranging the particles of the flowing sample in accordance with the particle size in the fractionating pipe; processing the sample as at least two fractions according to the particle size in the fractionating pipe; and measuring, with a sensor, at least one parameter of the ink of the at least one fraction.
 3. A method as claimed in claim 1, further comprising: processing the sample as at least two fractions by imaging the different particle sizes of the sample flowing in the fractionating pipe with a camera; and generating at least one image representative of at least one fraction with an image-processing unit from the images generated by the camera.
 4. A method as claimed in claim 1, further comprising: generating at least two fractions from the sample flowing in the fractionating pipe; imaging at least one fraction; and measuring at least one parameter of at least one added substance of at least one fraction from at least one image generated.
 5. A method as claimed in claim 1, further comprising: generating a cake from at least one fraction; imaging the cake generated from at least one fraction; and measuring at least one parameter of at least one added substance of at least one fraction from at least one image generated.
 6. A method as claimed in claim 1, further comprising measuring at least one parameter of at least one added substance of at least one fraction by spectrometry.
 7. A method as claimed in claim 1, further comprising: directing energy for achieving an acoustic response signal in the particles of a fraction; and measuring at least one parameter of at least one added substance of at least one fraction acoustically.
 8. A method as claimed in claim 1, further comprising measuring a parameter descriptive of the portion in the sample of at least one added substance adhered to the fibres.
 9. A method as claimed in claim 1, further comprising measuring a parameter descriptive of the portion in the sample of at least one added substance detached from the fibres.
 10. A method as claimed in claim 1, further comprising performing the measurement of the parameter by determining the difference between the distribution of at least one fraction measured after the desired subprocess and a predetermined distribution, wherein the predetermined distribution is descriptive of the desired distribution after the desired subprocess of the recycled fibre process.
 11. A method as claimed in claim 1, further comprising adding colouring agent to the sample for facilitating the measurement of the added substance.
 12. A method as claimed in claim 1, wherein the added substance is at least one of ink, plastic, wax, metal, or a hydrophobic substance.
 13. A measuring device for measuring recycled fibre pulp in a recycled fibre process, in the manufacture of which at least one of the following was used: paper, paperboard, pasteboard, and at least one added substance having been transferred to the surface of the paper, paperboard, pasteboard, the measuring device comprising: a fractionating pipe adapted to receive a sample from the recycled fibre pulp of the recycled fibre process and to arrange the particles of the flowing sample in accordance with the particle size, a sensor and a signal processing unit, wherein the measuring device is adapted to process the sample as at least two fractions according to the particle size in the fractionating pipe; the sensor is adapted to measure at least one fraction; the signal processing unit is adapted to receive a measurement signal from the sensor and to determine at least one parameter of the at least one added substance of the at least one measured fraction.
 14. A measuring device for measuring recycled fibre pulp in a recycled fibre process, in the manufacture of which at least one of the following was used: paper, paperboard, pasteboard, and ink having been transferred to the surface of the paper, paperboard, pasteboard, the measuring device comprising: a fractionating pipe adapted to receive a sample from the recycled fibre pulp of the recycled fibre process and to arrange the particles of the flowing sample in accordance with the particle size, a sensor and a signal processing unit, wherein the measuring device is adapted to process the sample as at least two fractions according to the particle size in the fractionating pipe; the sensor is adapted to measure at least one fraction; the signal processing unit is adapted to receive a measurement signal from the sensor and to determine at least one parameter of the ink of the at least one measured fraction.
 15. A measuring device as claimed in claim 13, wherein the measuring device is arranged to process the sample as at least two fractions in such a manner that a camera serving as the sensor is adapted to image the different particle sizes of the sample flowing in the fractionating pipe; and the signal processing unit is adapted to determine at least one parameter of at least one added substance from at least one image generated by the camera and representing at least one fraction.
 16. A measuring device as claimed in claim 13, wherein: the sensor is a camera adapted to image at least one fraction; and the signal processing unit is adapted to determine at least one parameter of at least one added substance from at least one image generated by the camera and representing at least one fraction.
 17. A measuring device as claimed in claim 16, wherein: the measuring device is adapted to generate a cake from at least one fraction; the camera is adapted to image said cake generated from at least one fraction; and the signal processing unit is adapted to determine at least one parameter of at least one added substance from at least one image generated by the camera and representing at least one fraction.
 18. A measuring device as claimed in claim 13, wherein: the sensor is a spectrometer adapted to measure at least one fraction; and the signal processing unit is adapted to determine at least one parameter of at least one added substance from a signal generated by the spectrometer and representing at least one fraction.
 19. A measuring device as claimed in claim 13, wherein: the measuring device comprises a source for directing energy to a fraction for achieving an acoustic response signal in the particles of the sample; the sensor is an acoustic sensor adapted to receive an acoustic signal originating from at least one fraction; and the signal processing unit is adapted to determine at least one parameter of at least one added substance from at least one signal generated by the sensor and representing at least one fraction.
 20. A measuring device as claimed in claim 13, wherein the signal processing unit is adapted to measure the parameter descriptive of the portion in the sample of at least one added substance adhered to the fibres.
 21. A measuring device as claimed in claim 13, wherein the signal processing unit is adapted to measure the parameter descriptive of the portion in the sample of at least one added substance detached from the fibres.
 22. A measuring device as claimed in claim 13, wherein the signal processing unit is adapted to measure the parameter by determining the difference between the distribution of at least one fraction measured after the desired subprocess and a predetermined distribution, and the predetermined distribution is descriptive of the desired distribution after the desired subprocess of the recycled fibre process.
 23. A measuring device as claimed in claim 13, wherein the measuring device is adapted to add colouring agent to the sample for facilitating the measurement of the added substance.
 24. A measuring device as claimed in claim 13, wherein the added substance is at least one of ink, plastic, wax, metal, or a hydrophobic substance. 